This invention relates to a novel intaglio printing plate that is particularly useful for printing changeable markings, such as bar-code markings representing serial numbers, on nonabsorbent surfaces. With the novel plate, the depressed or intaglio areas can be changed with each impression or transfer.
In U.S. patent application Ser. No. 534,103 filed Sept. 20, 1983, by P. M. Heyman now U.S. Pat. No. 4,473,008, there is described an intaglio printing plate with the above-described characteristics. That prior plate includes a body having a plate surface with an aperture therein, and a plurality of separately-movable bars in the aperture. Each bar has a flat end that is movable to a first position flush with the plate surface and to a second position depressed a small distance below the plate surface. Each bar is moved by a separate solenoid through a mechanical linkage. In operation, the solenoids move the bars to the desired positions, the plate is inked and the ink pattern is transferred, and then the cycle is repeated.
Because of the large number of solenoids required and because of the characteristics of solenoids, only clusters of small solenoids with relatively-low power are practical. Also, the nature of the ink and the large amount of contacting surface require a better mechanical arrangement to provide longer life and less maintenance for the inking plate.
It was suggested that the other end of each bar opposite the flat end be an inclined plane or taper. A sliding blade, driven pneumatically or hydraulically and having a mating taper, would be used to drive selected bars upward to the flush position, and metal springs would be used to maintain nonselected bars in the depressed position and, also, to return selected bars back to the depressed position. Most of the same disadvantages apply to this arrangement. Also individual springs require separate setup and adjustment.